High frequency tank circuits



J. W. CONKLIN El AL HIGH FREQUENCY CIRCUITS May 23, 1939.

3nventor$ l I a Filed July 24, 1937 w Patented May 23, 1939 2,159,782

2,159.7 HIGH FREQUENCY TANK CIRCUITS James W. Conklin, Audubon, and Robert Serrell, Haddoniield, N. 5., assignorc to Radio Corporation of America, a corporation of Delaware Application July 24, 1937, Serial No. 155,372

4 Claims. (cl- 17H!) Our invention relates to high frequency tank shorting bar and the armatures l5, ll increases circuits in which an adjustable transmission line the distributed capacity 01 the line.

forms the resonant circuit. More specifically, In Fig. 2 the transmission line 3| is connected the adjustable elements 01 the linev are so conto a pair of thermionic tubes 33, 35. The line UNITED STATES PATENT OFFICE 5 structed and arranged that the line has both 3| is comprised of elements arranged as follows:

coarse and fine adjustments; that the distributed on a mounting bar 31 are fastened a pair of paralcapacities are minimized; and that the losses due lei conductive members 39, 4|. A pair of hollow to adjustable contacts are made very low. conductors 43, 45 are slidably mounted on the One of the objects of our invention is to proparallel members 39, 4|, respectively. The hollow I I v'ide coarse and fine adjustments for tuning a conductors are tied together at one end by a m transmission line. member 41 into which is threaded an adjustment 8 I Another object is to provide means for tuning screw 49. The screw is rotatably mounted in the I I a resonant line over a wide range of frequencies mounting bar 31 and provided with thrust col- I [due to a minimization of distributed capacities. lars ll, 53.. The ends of the hollow conductors 4n additional object is to provide a transmis- 43, 45 opposite the member 41 are slotted and a I sion line with adjustable contacts which insure turned inwardly to make a low resistance slidably j low losses. I I contact as shown in Fig. 3. In place of a sliding In the accompanying drawing,- 4 contact, the hollow members may be connected Figure 1 is a schematic diagram representing to shoulders on the parallel members 4| by I jj two known methods of adjusting a transmission metallic expansion joints 5'! as shown in Fig. 4.

line, Intermediate the ends of the hollow members 43, 20 E Figure 2 is a schematic diagram illustrating one 45 is securely clamped a heavy shorting bar 59. embodiment of our invention. The embodiment of our invention illustrated Figures 3 and 4 are elevational views partly in Figs. 2, 3 and 4 offers substantial advantages i in section or two forms of adjustable contact, and over the prior art transmission lines represented Figure 5 is an elevational view of an element by Fig. 1. In our invention the sliding contacts Lot our invention appliedtothe water cooled anode (see Fig. 3) are arranged at a point near the I 3 of athermionic tube. minimum radio frequency current flow and there- Referring to Fig. 1, a transmission line I is contore the losses are minimized. It the expansion I. to a pair of thermionic tubes 3, 5. The joints (see Fig. 4) are used, no losses' due to H transmission line includes a pair of conductors sliding contacts willbeexperienced. The diame- I 1.9, a mounting and supporting member ll, an ter of the expansion joints is made preferably adjustable shorting bar l3, and a pair oi adjustsmall to hold the capacity between them as small yable. armatures I5, II. The shorting bar I: is as possible. Aconsiderable latitude of expansion actuated by a screw l9 which is threaded into the is not essential as the screw adjustment is only 1 bar. The screw is mounted within the member used for fine or vernier tuning. The coarse tun- II and is provided with thrust collars 2|, 2!. ing is eflected by moving the shorting bar 59. 1 ;,In practice it is customary to use either an ad- The shorting bar can be made of copper or 'j ustrnent of the capacity of the armatures I5, I! the like or suflicient dimensions to insure excel- .or the adjustment of the shortingbar ii to vary lent conductivity. The bar 59 can be made to the resonant characteristics of the line. We have tightly clamp the hollow members 43-45 over a I found that both of these adjustments ofl'er certain wide area; thus insuring an excellent high fredimculties. The capacity adjustment is objecquency contact. .tionable because it is limited in range, due to the The shorting bar 59 may be grounded for radio fact that the capacity is located near points of frequency currents. The entire device may be 5 maximum potential, and the adjustable screws 25. supported by the mounting bar 31.

I 1 )1 21 supporting the armatures increase the distribour invention may be applied to the water I ,uted capac y f the Unit Furthermore, h cooled anode of a thermionic tube as shown'in l ting screws 25, 21 a at high radio quency Fig. 5. Airagment 6| or the envelope of the thern potentials and therefore diflicult to adjust, even mionic tube terminates in the metal jacket of the with an insulated screw driver. The shorting anode 63. The inner conductor of a concentric bar is objectionable because the slidable contacts line is made of pipes 55, 51 which are preferably are at a point near the maximum high frequency coaxially arranged. The ends 69-" of the pipes current flow and therefore cause highlosses, and 55, 51 are flared to form jackets around the anode :because the portion of the screw it between the 54. Aflange II on the anode 531s clamped to the u flared portion or the pipe II by a coupling 15 which makes the jackets water tight. Water is sent through space between the pipes around the Jackets and discharged through the inner pipe as shown by the arrow H. The fiow of water, which cools the anode, may be made from the inner pipes to the space between the inner and outer pipes. Fluids other than water may be used.

Thus, we have described an adjustable transmission line with means for obtaining coarse and fine adjustments of the effective length of the line. The transmission line oi our invention has low loss adjustable contacts, and a minimum 0! distributed capacity. The invention may be employed with air or water cooled tubes. In the embodiment illustrated, we have removed the deleterious eflect of the adjustable elements from the radio frequency field.

We claim as our invention:

1. A transmission line including a pair of conductors, means for mounting said conductors in spaced and parallel relation, a pair of hollow conductors adjustably mounted over said parallel conductors, semipermanent means for efiiciently shorting said hollow conductors at substantially the points of maximum high frequency current flow and to provide a coarse adjustment of said line, means for effectively slidably contacting said parallel and hollow conductors at substantially the points of minimum high frequency current flow, means for adjusting the position of said hollow conductors on said parallel conductors to provide a Vernier adjustment of said line.

2. A high efliciency resonant line comprising a pair of conductors substantially more than a quarter wavelength long, means for mounting said conductors in spaced and parallel relation, two hollow conductors, one adjustably enclosing a substantial portion of each 01 said pair of conductors.

means connecting one pair of adjacent ends of said hollow conductors whereby they may be moved simultaneously along said pair of conductors, semipermanent tuning means eificiently shorting said hollow conductors at substantially s the points of maximum high frequency current flow, said tuning means providing a normally fixed connection of low loss, means for eii'ectively contacting said parallel and said hollow conductors at substantially the points of minimum high frel0 quency current flow, and means including said connecting means for adjusting the position of said hollow conductors on said parallel conductors to provide a vernier adjustment of said line.

3. A device of the character of claim '2 in which 15 said means for effectively contacting said parallel and said hollow conductors is an expansion memher.

4. A high efllciency resonant line comprising a pair of conductors substantially more than a so quarter wavelength long, a first member connecting adjacent ends of said conductors for mounting said conductors in spaced and parallel relation, two hollow conductors, one slidably mounted on and enclosing a substantial portion of the length 25 of each of said pair of conductors; a second member connecting said hollow conductors at the ends which are adjacent said first members; a semipermanent tuning bar efficiently shorting said hollow conductors at substantially the points of .0 maximum high frequency current flow, said tuning bar providing a normally fixed connection oi low loss; and an adjusting screw engaging said first and second connecting members for adjusting the position of said hollow conductors on said ll parallel conductors.

JAMES W. CONKLIN. ROBERT SERRELL. 

